Assistant Professor of Medicine (Blood and Marrow Transplantation) at the Stanford University Medical Center

Medicine - Blood & Marrow Transplantation

Bio

Bio

Research focus in T cell immunotherapy and T cell immune monitoring using high-throughput sequencing and genomic approaches, with an emphasis on hematopoietic stem cell transplantation, the treatment of graft-versus-host disease and immune tolerance induction.

Research & Scholarship

Current Research and Scholarly Interests

Research focus in T cell immunotherapy and T cell immune monitoring using high-throughput sequencing and genomic approaches, with an emphasis on hematopoietic stem cell transplantation, the treatment of graft-versus-host disease and immune tolerance induction.

Clinical Trials

Allogeneic stem cell transplantation (transplant of blood cells from another individual) is
a treatment option for patients with Myelodysplasia or Myeloproliferative Disorders. During
the course of this study, we will attempt to learn whether a particular type of blood cell,
called a Cytokine Induced Killer (CIK) cell may add benefit to allogeneic stem cell
transplantation. CIK cells are present in small quantities in the bloodstream but their
numbers can be expanded after a brief period of nurturing in a laboratory.

Stanford is currently not accepting patients for this trial.For more information, please contact Physician Referrals, 650-723-0822.

This phase Ib trial studies the side effects and best dose of neihulizumab in treating
patients with acute graft-versus-host disease (aGVHD) that does not respond to steroid
treatment undergoing stem cell transplant. Sometimes after a stem cell transplant, the
transplanted cells from a donor can make an immune response against the body's normal cells
(called GVHD). Monoclonal antibodies, such as neihulizumab, may be an effective treatment
for GVHD by binding to a protein found on the surface of immune cells (T cells).

Stanford is currently not accepting patients for this trial.For more information, please contact Joanne Otani, 650-721-2372.

This phase I trial studies the side effects and best dose of donor regulatory T cells in
treating patients with graft-versus-host disease affecting the liver or gastrointestinal
organs (visceral) within 100 days (acute) after undergoing a stem cell transplant.
Graft-versus-host disease occurs when donor immune cells infused in a stem cell transplant
attack the gut, skin, liver, or other organ systems of the patient. Regulatory T cells are a
type of immune cell that may be able to reduce the attack of the donor's immune cells on the
patient's normal cells and help treat graft-vs-host disease.

Stanford is currently not accepting patients for this trial.For more information, please contact Joanne Otani, 650-721-2372.

Abstract

Sex-mismatched hematopoietic cell transplantation is linked to increased graft-versus-host disease and mortality in myeloablative conditioning. Here we evaluated outcomes of 1,041 adult transplant recipients at two centers between 2006 and 2013 and investigated how the effect of sex-mismatching differed in myeloablative, reduced-intensity, and non-myeloablative total lymphoid irradiation with anti-thymocyte globulin conditioning. Among patients who underwent myeloablative conditioning, male recipients with female donors had increased chronic graft-versus-host disease (hazard ratio 1.83, P<0.01), increased non-relapse mortality (hazard ratio 1.84, P=0.022) and inferior overall survival (hazard ratio 1.59, P=0.018). In contrast, among patients who received reduced-intensity conditioning, male recipients with female donors had increased acute graft-versus-host disease (hazard ratio 1.96, P<0.01) but no difference in non-relapse mortality or overall survival. Among the patients who underwent total lymphoid irradiation with anti-thymocyte globulin, male recipients with female donors showed no increase in graft-versus-host disease or non-relapse mortality. Notably, only in the cohort receiving total lymphoid irradiation with anti-thymocyte globulin were male recipients with female donors significantly associated with reduced relapse (hazard ratio 0.64, P<0.01), and allo-antibody responses against H-Y antigens were predictive of reduced relapse. In the cohort given total lymphoid irradiation with anti-thymocyte globulin, the graft-versus-leukemia effect resulted in superior overall survival in recipients of sex-mismatched grafts (HR 0.69, P=0.037). In addition, only in the cohort treated with total lymphoid irradiation with anti-thymocyte globulin were female recipients with male donors associated with reduced relapse (hazard ratio 0.59, P<0.01) and superior survival (hazard ratio 0.61, P=0.014) compared with sex-matched pairs. We conclude that the risks and benefits of sex-mismatched transplants appear to differ according to conditioning strategy and this could affect donor selection.

Abstract

Graft-versus-host disease (GVHD) is driven by extensive activation and proliferation of alloreactive donor T cells causing significant morbidity and mortality following allogeneic hematopoietic cell transplantation (HCT). Invariant natural killer T (iNKT) cells are a potent immunoregulatory T-cell subset in both humans and mice. Here, we explored the role of adoptively transferred third party CD4(+) iNKT cells for protection from lethal GVHD in a murine model of allogeneic HCT across major histocompatibility barriers. We found that low numbers of CD4(+) iNKT cells from third party mice resulted in a significant survival benefit with retained graft-versus-tumor (GVT) effects. In vivo expansion of alloreactive T cells was diminished while displaying a Th2-biased phenotype. Notably, CD4(+) iNKT cells from third party mice were as protective as CD4(+) iNKT cells from donor mice although third party CD4(+) iNKT cells were rejected early after allogeneic HCT. Adoptive transfer of third party CD4(+) iNKT cells resulted in a robust expansion of donor CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) that were required for protection from lethal GVHD. However, in vivo depletion of myeloid-derived suppressor cells (MDSCs) abrogated both Treg expansion and protection from lethal GVHD. Despite the fact that iNKT cells are a rare cell population, the almost unlimited third party availability and feasibility of in vitro expansion provide the basis for clinical translation.

Abstract

The exact nature of the immune response elicited by autologous-induced pluripotent stem cell (iPSC) progeny is still not well understood. Here we show in murine models that autologous iPSC-derived endothelial cells (iECs) elicit an immune response that resembles the one against a comparable somatic cell, the aortic endothelial cell (AEC). These cells exhibit long-term survival in vivo and prompt a tolerogenic immune response characterized by elevated IL-10 expression. In contrast, undifferentiated iPSCs elicit a very different immune response with high lymphocytic infiltration and elevated IFN-γ, granzyme-B and perforin intragraft. Furthermore, the clonal structure of infiltrating T cells from iEC grafts is statistically indistinguishable from that of AECs, but is different from that of undifferentiated iPSC grafts. Taken together, our results indicate that the differentiation of iPSCs results in a loss of immunogenicity and leads to the induction of tolerance, despite expected antigen expression differences between iPSC-derived versus original somatic cells.

Abstract

There is lack of consensus regarding whether both upper and lower endoscopic examinations are required for diagnosis of gastrointestinal acute graft versus host disease (GI-AGVHD).To evaluate the impact of endoscopic procedures on the diagnosis of GI-AGVHD.We performed a retrospective case-control study of recipients of allogeneic haematopoetic cell transplant (HCT) from 2000 to 2011, who presented with GI symptoms between 20 and 125 days post-HCT. GI-AGVHD status was based on the National Institutes of Health (NIH) clinical grading system.One hundred and twenty-nine clinical GI-AGVHD cases and 184 controls underwent endoscopic examinations. Diarrhoea was present in 73% of cases and 38% of controls (P < 0.0001); 99% of patients with nausea ± vomiting and diarrhoea underwent bidirectional endoscopy. Histology had a sensitivity of 92% and specificity of 91% compared to the clinical criteria. The sensitivity for GI-AGVHD was 80% or greater when upper endoscopy (EGD) was performed with either sigmoidoscopy or colonoscopy, or if lower endoscopic examinations were performed alone. The sensitivity of EGD alone was only 48% (P = 0.003). Sensitivity was highest with biopsy of the terminal ileum (79%), followed by the ascending (74%), transverse/descending (73%) and sigmoid colons (69%). Diagnostic yield for cytomegalovirus (CMV) infection was equivalent for biopsies from both upper and lower GI tracts. Patients found to have concurrent GI-AGVHD and CMV infection (N = 18) had a poorer overall prognosis.In patients post-HCT with GI symptoms, sigmoidoscopy alone had equivalent diagnostic yield for GI-AGVHD and CMV infection, compared with the addition of EGD or performance of full colonoscopy.

Abstract

Steroid refractory gastrointestinal (GI) acute graft versus host disease (aGVHD) is a major cause of mortality in hematopoietic stem cell transplantation (HCT) without immune markers to establish a diagnosis or guide therapy. We found that T cell receptor β (TCRβ) CDR3 repertoire sequencing reveals patterns that could eventually serve as a disease biomarker of T cell alloreactivity in aGVHD. We identified T cell clones in GI biopsies in a heterogeneous group of 15 allogeneic HCT patients with GI aGVHD symptoms. Seven steroid-refractory aGVHD patients showed a more conserved TCRβ clonal structure between different biopsy sites in the GI tract than eight primary-therapy responsive patients. Tracking GI clones identified at endoscopy longitudinally in the blood also revealed an increased clonal expansion in patients with steroid-refractory disease. Immune repertoire sequencing-based methods could enable a novel personalized way to guide diagnosis and therapy in diseases where T cell activity is a major determinant.

Abstract

T cell Ig-like mucin-like-1 (TIM-1) is an important asthma susceptibility gene, but the immunological mechanisms by which TIM-1 functions remain uncertain. TIM-1 is also a receptor for phosphatidylserine (PtdSer), an important marker of cells undergoing programmed cell death, or apoptosis. We now demonstrate that NKT cells constitutively express TIM-1 and become activated by apoptotic cells expressing PtdSer. TIM-1 recognition of PtdSer induced NKT cell activation, proliferation, and cytokine production. Moreover, the induction of apoptosis in airway epithelial cells activated pulmonary NKT cells and unexpectedly resulted in airway hyperreactivity, a cardinal feature of asthma, in an NKT cell-dependent and TIM-1-dependent fashion. These results suggest that TIM-1 serves as a pattern recognition receptor on NKT cells that senses PtdSer on apoptotic cells as a damage-associated molecular pattern. Furthermore, these results provide evidence for a novel innate pathway that results in airway hyperreactivity and may help to explain how TIM-1 and NKT cells regulate asthma.

Abstract

Allergic asthma is characterized by Th2-driven eosinophilic airway inflammation and by a central feature called airway hyperreactivity (AHR), development of which requires the presence of classical type I invariant NK T (iNKT) cells. Allergen-induced AHR, however, develops in beta(2)-microglobulin (beta(2)m)(-/-) mice, which lack classical iNKT cells, suggesting that in some situations iNKT cells may be dispensable for the development of AHR. In contrast, our studies now suggest that a CD1d-restricted, NK1.1(+) noninvariant TCR NKT cell population is present in beta(2)m(-/-) mice and is responsible for the development of AHR but not for Th2 responses. Furthermore, treatment of beta(2)m(-/-) mice with anti-CD1d mAb or anti-NK1.1 mAb unexpectedly abolished allergen-induced AHR. The CD1-restricted NKT cells in these mice, which failed to respond to alpha-galactosylceramide and which therefore were not classical type I iNKT cells, appear to represent an NKT cell subset restricted by a beta(2)m-independent form of CD1d. These results indicate that, although classical type I iNKT cells are normally required for the development of AHR, under different circumstances other NKT cell subsets, including nonclassical NKT cells, may substitute for classical iNKT cells and induce AHR.

Abstract

The development of airway hyperreactivity (AHR), a cardinal feature of asthma, requires the presence of invariant NKT (iNKT) cells. In a mouse model of asthma, we demonstrated that the induction of AHR required ICOS costimulation of iNKT cells. ICOS was highly expressed on both naive and activated iNKT cells, and expression of ICOS was greater on the CD4(+) iNKT than on CD4(-) iNKT cells. Furthermore, the number of CD4(+) iNKT cells was significantly lower in spleens and livers of ICOS(-/-) and ICOSL(-/-) mice, and the remaining iNKT cells in ICOS(-/-) mice were dysfunctional and failed to reconstitute AHR when adoptively transferred into iNKT cell-deficient Jalpha18(-/-) mice. In addition, direct activation of iNKT cells with alpha-GalCer, which induced AHR in wild-type mice, failed to induce AHR in ICOS(-/-) mice. The failure of ICOS(-/-) iNKT cells to induce AHR was due in part to an inability of the ICOS(-/-) iNKT cells to produce IL-4 and IL-13 on activation. Moreover, survival of wild-type iNKT cells transferred into ICOSL(-/-) mice was greatly reduced due to the induction of apoptosis. These results indicate that ICOS costimulation plays a major role in induction of AHR by iNKT cells and is required for CD4(+) iNKT cell function, homeostasis, and survival in the periphery.

Abstract

Exposure to ozone, which is a major component of air pollution, induces a form of asthma that occurs in the absence of adaptive immunity. Although ozone-induced asthma is characterized by airway neutrophilia, and not eosinophilia, it is nevertheless associated with airway hyperreactivity (AHR), which is a cardinal feature of asthma. Because AHR induced by allergens requires the presence of natural killer T (NKT) cells, we asked whether ozone-induced AHR had similar requirements. We found that repeated exposure of wild-type (WT) mice to ozone induced severe AHR associated with an increase in airway NKT cells, neutrophils, and macrophages. Surprisingly, NKT cell-deficient (CD1d(-/-) and Jalpha18(-/-)) mice failed to develop ozone-induced AHR. Further, treatment of WT mice with an anti-CD1d mAb blocked NKT cell activation and prevented ozone-induced AHR. Moreover, ozone-induced, but not allergen-induced, AHR was associated with NKT cells producing interleukin (IL)-17, and failed to occur in IL-17(-/-) mice nor in WT mice treated with anti-IL-17 mAb. Thus, ozone exposure induces AHR that requires the presence of NKT cells and IL-17 production. Because NKT cells are required for the development of two very disparate forms of AHR (ozone- and allergen-induced), our results strongly suggest that NKT cells mediate a unifying pathogenic mechanism for several distinct forms of asthma, and represent a unique target for effective asthma therapy.

Abstract

Asthma is an immunological disease with multiple inflammatory and clinical phenotypes, characterized by symptoms of wheezing, shortness of breath, and coughing due to airway hyperreactivity (AHR) and reversible airway obstruction. In allergic asthma, the most common form of asthma, airway inflammation is mediated by adaptive immune recognition of protein allergens by Th2 cells, resulting in airway eosinophilia. However, in other forms of asthma, inflammation is associated with immune responses to respiratory infections and airway neutrophilia. A central feature common to all forms of asthma is AHR, the heightened responsiveness of the airways to nonspecific stimuli. AHR has been shown recently in animal models of asthma to require the presence of CD1d-restricted, invariant T cell receptor-positive, natural killer T (iNKT) cells. Although allergen-specific Th2 cells and iNKT cells have many phenotypic similarities (e.g., expression of CD4 and production of Th2 cytokines), they have complementary activities, such as production of Th2 cytokines under different conditions, differential sensitivity to corticosteroids, and responsiveness to different classes of antigen (proteins versus glycolipids). We hypothesize that Th2 cells and iNKT cells interact synergistically to induce asthma but that different forms of asthma result from distinct roles of CD4(+) iNKT cells versus Th2 cells.

Abstract

Sudden discontinuation of serotonin reuptake inhibitors (SRI) can lead to a number of psychological (e.g., nervousness, anxiety, crying spells, psychomotor agitation, irritability, depersonalization, decreased mood, memory disturbances, confusion, decreased concentration, and/or slowed thinking) and somatic (e.g., nausea, dizziness, headache) symptoms. Recent studies have shown that withdrawal symptoms are common with paroxetine, venlafaxine and fluvoxamine, but relatively rare and mild with fluoxetine cessation, likely as a result of its longer half-life. We report an unusual case of a patient who developed delirium after abrupt discontinuation of fluoxetine.

Abstract

iNKT cells are required for the induction of airway hyperreactivity (AHR), a cardinal feature of asthma, but how iNKT cells traffic to the lungs to induce AHR has not been previously studied. Using several models of asthma, we demonstrated that iNKT cells required the chemokine receptor CCR4 for pulmonary localization and for the induction of AHR. In both allergen-induced and glycolipid-induced models of AHR, wild-type but not CCR4-/- mice developed AHR. Furthermore, adoptive transfer of wild-type but not CCR4-/- iNKT cells reconstituted AHR in iNKT cell-deficient mice. Moreover, we specifically tracked CCR4-/- vs wild-type iNKT cells in CCR4-/-:wild-type mixed BM chimeric mice in the resting state, and when AHR was induced by protein allergen or glycolipid. Using this unique model, we showed that both iNKT cells and conventional T cells required CCR4 for competitive localization into the bronchoalveolar lavage/airways compartment. These results establish for the first time that the pulmonary localization of iNKT cells critical for the induction of AHR requires CCR4 expression by iNKT cells.

Abstract

Recent studies indicate that invariant TCR+ CD1d-restricted natural killer T (iNKT) cells play an important role in regulating the development of asthma and allergy. iNKT cells can function to skew adaptive immunity toward Th2 responses, or can act directly as effector cells at mucosal surfaces in diseases such as ulcerative colitis and bronchial asthma. In mouse models of asthma, NKT cell-deficient strains fail to develop allergen-induced airway hyperreactivity (AHR), a cardinal feature of asthma, and NKT cells are found in the lungs of patients with chronic asthma, suggesting a critical role for NKT cells in the development of AHR. However, much work remains in characterizing iNKT cells and their function in asthma, and in understanding the relationship between the iNKT cells and conventional CD4+ T cells.

Abstract

Invariant T-cell receptor-positive natural killer (iNKT) cells have been shown to be essential for the development of allergen-induced airway hyperreactivity (AHR).We examined the role of iNKT cells in allergic skin inflammation using a murine model of atopic dermatitis (AD) elicited by epicutaneous sensitization with ovalbumin (OVA).Wild-type (WT) and natural killer T-cell-deficient CD1d-/- mice were epicutaneously sensitized with OVA or normal saline and challenged with aerosolized OVA. iNKT cells in skin and bronchoalveolar lavage fluid were analyzed by fluorescence-activated cell sorting, and cytokine mRNA levels were measured by quantitative RT-PCR. AHR to methacholine was measured after OVA inhalation.Skin infiltration by eosinophils and CD4+ cells and expression of mRNA encoding IL-4 and IL-13 in OVA-sensitized skin were similar in WT and CD1d-/- mice. No significant increase in iNKT cells was detectable in epicutaneously sensitized skin. In contrast, iNKT cells were found in the bronchoalveolar lavage fluid from OVA-challenged epicutaneously sensitized WT mice, but not CD1d-/- mice. Epicutaneously sensitized CD1d-/- mice had an impaired expression of IL-4, IL-5, and IL-13 mRNA in the lung and failed to develop AHR in response to airway challenge with OVA.These results demonstrate that iNKT cells are not required for allergic skin inflammation in a murine model of AD, in contrast with airway inflammation, in which iNKT cells are essential.Understanding the potential role of iNKT cells in AD will allow us to have a more specific target for therapeutic use.

Abstract

Asthma is an inflammatory lung disease, in which conventional CD4+ T cells producing IL-4/IL-13 appear to play an obligatory pathogenic role. Here we show, in a mouse model of asthma, that activation of pulmonary IL-4/IL-13 producing invariant TCR+ CD1d-restricted natural killer T (NKT) cells is sufficient for the development of airway hyperreactivity (AHR), a cardinal feature of asthma, in the absence of conventional CD4+ T cells and adaptive immunity. Respiratory administration of glycolipid antigens that specifically activate NKT cells (alpha-GalactosylCeramide and a Sphingomonas bacterial glycolipid) rapidly induced AHR and inflammation typically associated with protein allergen administration. Naïve MHC class II-deficient mice, which lack conventional CD4+ T but have NKT cells, showed exaggerated baseline AHR and, when challenged with alpha-GalactosylCeramide, demonstrated even greater AHR. These studies demonstrate an expanded role for NKT cells, in which NKT cells not only produce cytokines that influence adaptive immunity but also function as critical effector cells that can induce AHR. These results suggest that NKT cells responding to glycolipid antigens, as well as conventional CD4+ T cells responding to peptide antigens, may be synergistic in the induction of AHR, although in some cases, each may independently induce AHR.

Abstract

Natural genetic variants at the phosphoglucose isomerase, PGI, gene differ in spatial patterning of their polymorphism among species complexes of Colias butterflies in North America. In both lowland and alpine complexes, molecular-functional properties of the polymorphic genotypes can be used to predict genotype-specific adult flight performances and resulting large genotypic differences in adult fitness components. In the lowland species complex, there is striking uniformity of PGI polymorph frequencies at a number of sites across the American West; this fits with earlier findings of strong, similar differences in fitness components over this range. In an alpine complex, Colias meadii shows similar uniformity of PGI frequencies within habitat types, either montane steppe or alpine tundra, over several hundred kilometres in the absence of dispersal. At the same time, large shifts (10-20%) in frequency of the most common alleles occur between steppe and tundra populations, whether these are isolated or, as in some cases, are in contact and exchange many dispersing adults each generation. Data on male mating success of common C. meadii PGI genotypes in steppe and tundra show heterozygote advantage in both habitat types, with shifts in relative homozygote disadvantage between habitats which are consistent with observed frequency differences. Nonadaptive explanations for this situation are rejected, and alternative, thermal-ecology-based adaptive hypotheses are proposed for later experimental test. These findings show that strong local selection may dominate dispersal as an evolutionary agent, whether or not dispersal is present, and that selection may often be the major force promoting 'cohesion' of species over long distances. This case offers new opportunities for integrating studies of molecular structure and function with ecological aspects of natural selection in the wild, both within and among species.

Abstract

Using natural killer T (NKT) cell-deficient mice, we show here that allergen-induced airway hyperreactivity (AHR), a cardinal feature of asthma, does not develop in the absence of V(alpha)14i NKT cells. The failure of NKT cell-deficient mice to develop AHR is not due to an inability of these mice to produce type 2 T-helper (Th2) responses because NKT cell-deficient mice that are immunized subcutaneously at non-mucosal sites produce normal Th2-biased responses. The failure to develop AHR can be reversed by the adoptive transfer of tetramer-purified NKT cells producing interleukin (IL)-4 and IL-13 to Ja281(-/-) mice, which lack the invariant T-cell receptor (TCR) of NKT cells, or by the administration to Cd1d(-/-) mice of recombinant IL-13, which directly affects airway smooth muscle cells. Thus, pulmonary V(alpha)14i NKT cells crucially regulate the development of asthma and Th2-biased respiratory immunity against nominal exogenous antigens. Therapies that target V(alpha)14i NKT cells may be clinically effective in limiting the development of AHR and asthma.

Abstract

T(H)2 cells play a critical role in the pathogenesis of asthma, but the precise immunologic mechanisms that inhibit T(H)2 cell function in vivo are not well understood.The purpose of our studies was to determine whether T cells producing IL-10 regulate the development of asthma.We used gene therapy to generate ovalbumin-specific CD4 T-helper cells to express IL-10, and we examined their capacity to regulate allergen-induced airway hyperreactivity.We demonstrated that the CD4 T-helper cells engineered to express IL-10 abolished airway hyperreactivity and airway eosinophilia in BALB/c mice sensitized and challenged with ovalbumin and in SCID mice reconstituted with ovalbumin-specific T(H)2 effector cells. The inhibitory effect of the IL-10-secreting T-helper cells was accompanied by the presence of increased quantities of IL-10 in the bronchoalveolar lavage fluid, was antigen-specific, and was reversed by neutralization of IL-10. Moreover, neutralization of IL-10 by administration of anti-IL-10 mAb in mice sensitized and challenged with ovalbumin seriously exacerbated airway hyperreactivity and airway inflammation.Our results demonstrate that T cells secreting IL-10 in the respiratory mucosa can indeed regulate T(H)2-induced airway hyperreactivity and inflammation, and they strongly suggest that IL-10 plays an important inhibitory role in allergic asthma.

Abstract

Asthma is caused by T-helper cell 2 (Th2)-driven immune responses, but the immunological mechanisms that protect against asthma development are poorly understood. T-cell tolerance, induced by respiratory exposure to allergen, can inhibit the development of airway hyperreactivity (AHR), a cardinal feature of asthma, and we show here that regulatory T (T(R)) cells can mediate this protective effect. Mature pulmonary dendritic cells in the bronchial lymph nodes of mice exposed to respiratory allergen induced the development of T(R) cells, in a process that required T-cell costimulation via the inducible costimulator (ICOS-ICOS-ligand pathway. The T(R) cells produced IL-10, and had potent inhibitory activity; when adoptively transferred into sensitized mice, T(R) cells blocked the development of AHR. Both the development and the inhibitory function of regulatory cells were dependent on the presence of IL-10 and on ICOS-ICOS-ligand interactions. These studies demonstrate that T(R) cells and the ICOS-ICOS-ligand signaling pathway are critically involved in respiratory tolerance and in downregulating pulmonary inflammation in asthma.